Since the advent of AIDS (acquired immunodeficiency syndrome), the need for effective treatments for viral infections has become urgent. AIDS is caused by human immunodeficiency virus 1 (HIV-1). The initial pathogenic event is the binding of HIV-1 to the CD4 receptor on a subset of T cells and monocyte-macrophages. Fauci et al., Ann. Intern. Med., 114, 678-693 (1991) (summary of a National Institutes of Health Conference). The virus interacts with the human immune system, and the ultimate consequence of this interaction is a profound immunosuppression resulting from the quantitative depletion and functional abnormalities of the CD4 T-cell subset. Id. Mononuclear phagocytes may play a role in the pathogenesis of HIV-1 infection by serving as reservoirs of the virus. Id. Of note is the fact that monocytes in the peripheral blood of HIV-1-infected individuals are rarely infected in vivo, whereas infected tissue macrophages may play a role in organ-specific HIV-1-related pathogenesis. Id.
One drug that has been approved by the Food and Drug Administration (FDA) for the treatment of AIDS is 3'-azido-2',3'-dideoxy-thymidine (zidovudine, azidothymidine, AZT) which inhibits HIV-1 replication by acting at the level of reverse transcriptase. However, AZT causes serious side effects, such as bone marrow suppression, and it is poorly tolerated in a high proportion of patients. Yarchoan et al., Immunol. Today, 11, 327-33 (1990). Also, the beneficial effects of AZT have been reported to abate in 12-18 months. Chase, "Doctors and Patients Hope AZT Will Help Stave Off AIDS," Wall Street Journal, Apr. 28, 1988, page 14, col. 1.
The FDA has also approved 2',3'-dideoxyinosine (DDI) for the treatment of AIDS in patients who cannot tolerate AZT or for whom AZT is no longer effective. DDI has been found efficacious and safe in the short term, but its long term effects are not yet known. Chem. Eng. News, Oct. 14, 1991, at 17.
Another drug for the treatment of AIDS is ampligen. Ampligen is a mispaired double-stranded RNA. It increases antiviral activity by stimulating interferon production, activating natural killer cells, and augmenting an internal cellular antiviral mechanism. Montefiori et al., Proc. Nat'l Acad. Sci. U.S.A., 84, 2985-89 (1987) and Dagani, Chem. Eng. News, Nov. 23, 1987, at 41-49.
Other possible therapeutic approaches for the treatment of AIDS are discussed in Yarchoan et al., Immunol. Today, 11, 327-33 (1990); Dagani, Chem. Eng. News, Nov. 23, 1987, at 41-49.
C-reactive protein (CRP) was first described by Tillett and Francis [J. Exp. Med., 52, 561-71 (1930)] who observed that sera from acutely ill patients precipitated with the C-polysaccharide of the cell wall of Streptococcus pneumoniae. Others subsequently identified the reactive serum factor as protein, hence the designation "C-reactive protein."
In addition to binding to pneumococcal C-polysaccharide, CRP binds to: 1) phosphate monoesters, including particularly phosphorylcholine; 2) other cell wall polysaccharides containing phosphorylcholine; 3) phosphatidyl choline (lecithin); 4) fibronectin; 5) chromatin; 6) histones; and 7) the 70 kDa polypeptide of the U1 small nuclear ribonucleoprotein. Kilpatrick and Volanakis, Immunol, Res., 10, 43-53 (1991). Several laboratories have also reported the binding of CRP to galactose-containing polysaccharides. Id. However, one laboratory has reported that CRP binds to trace phosphate groups that are minor constituents of one particular galactan, making it is unclear whether CRP binding to other galactans is also directed to phosphate residues or to carbohydrate determinants. Id.
Atono et al., Gastroenterologia Japonica, 24, 655-662 (1989) teaches that the level of serum CRP is markedly increased in patients with acute hepatitis type A and type B, especially in type A, but decreases rapidly during the convalescent phase. The article also reports that the CRP level is generally low in non-A, non-B hepatitis in both the acute and convalescent phases.
Putto et al., Archives of Disease in Childhood, 61, 24-29 (1986) reports the results of measurements of the level of CRP in febrile children suffering from bacterial and viral infections. If the duration of the illness was more than 12 hours and the CRP level was less than 20 mg/ml, all children investigated had viral or probable viral infections. Some children with CRP levels of 20 mg/ml or less had invasive bacterial infections, but they had been sick for 12 hours or less. CRP levels between 20 mg/ml and 40 mg/ml were recorded in children with both viral and bacterial infections. A CRP value greater than, or equal to, 40 mg/ml detected 79% of bacterial infections with 90% specificity.
To Applicant's knowledge, there have been no reports of CRP binding to viruses, contributing to the phagocytosis of viruses, or otherwise being able to neutralize viruses. Moreover, Applicant is not aware of any reports of CRP being used to treat viral infections.
Much of the study of CRP has been directed to determining its role in bacterial infections. For instance, Xia et al., FASEB J., 5, A1628 (1991) describes experiments designed to explore the role of CRP in endotoxin shock. A chimeric gene coding for rabbit CRP under the control of an inducible promoter (inducible in response to demand for gluconeogenesis) was introduced into mice. In contrast to most other vertebrates, mice synthesize only trace amounts of endogenous CRP, even during an acute phase response. When the chimeric gene was introduced into the mice, rabbit CRP was expressed in response to demand for gluconeogenesis. Further, it was found that 75% of mice expressing high levels of rabbit CRP following induction of gluconeogenesis survived treatment with 350-400 .mu.g of endotoxin, as compared to 27% survival for animals in which rabbit CRP synthesis had been suppressed by inhibiting gluconeogenesis. The authors speculate that CRP may play a role in natural defense against endotoxin shock, although CRP is not known to bind endotoxin.
Mold et al., Infection and Immunity, 38, 392-395 (1982) reports that CRP binding can lead to complement activation and, in the presence of complement, enhancement of opsonization of C-polysaccharide-sensitized erythrocytes and type 27 S. pneumoniae. The article further reports that injection of CRP increased survival in mice challenged with type 3 or type 4 S. pneumoniae. Finally, the authors describe test results from which they conclude that CRP binds to a small group of potentially pathogenic gram-positive bacteria (S. pneumoniae, Streptococcus viridans, and one isolate of Staphylococcus aureus), but does not bind to gram-negative bacteria or to other gram-positive bacteria. They, therefore, postulate that the ability of CRP to enhance opsonization and contribute to host defense may be specific for infection with S. pneumoniae.
Similarly, Mold et al., Ann. N.Y. Acad. Sci., 389, 251-62 (1982) reports that CRP can act as an opsonin in the presence of complement. However, the article teaches that CRP does not bind to gram-negative bacteria and binds to only some gram-positive organisms. For those gram-positive bacteria to which CRP binds, the effectivenss of CRP as an opsonin varied depending on the species. Finally, the article reports that CRP protected mice from type 3 and type 4 S. pneumoniae infection.
Nakayama et al., Clin. Exp. Immunol., 54, 319-26 (1983) also teaches that CRP protects against lethal infection with type 3 or type 4 S. pneumoniae. The article further teaches that CRP did not protect against a similar dose of Salmonella typhimurium LT2.
Horowitz et al., J. Immunol., 138, 2598-2603 (1987) describes the effects of CRP in mice with a X-linked immunodeficiency ("xid mice") which prevents the mice from making antibodies to polysaccharide antigens. In these mice, CRP provided protection against infection with type 3 S. pneumonia and acted by clearing the bacteria from the blood. However, CRP was not completely protective at higher doses of S. pneumoniae. Since CRP provides complete protection against these doses in normal mice, the authors speculated that CRP's function is to slow the development of pneumococcal bacteremia until protective antibodies to capsular polysaccharide can be produced. C3 depletion decreased or abrogated the protective effects of CRP in xid mice, but not in normal mice.
Nakayama et al., J. Immunol., 132, 1336-40 1984) reports the results of injecting mice with CRP and then immunizing them with type 3 S. pneumococci. The result was a diminished antibody response to the phosphorylcholine determinants on the bacteria which varied with the dose of CRP. However, antibodies were formed to other antigenic determinants on the S. pneumococci.
Hokama et al., J. Bacteriology, 83, 1017-1024 (1962) reports that carbonyl iron spherules, Diplococcus pneumoniae types IIs and XXVIIs and Serratia marcescens were phagocytosed more rapidly and in greater numbers by leukocytes of normal human blood after incubation with CRP. Similarly, Kindmark, Clin. Exp. Immunol., 8, 941-48 (1971) reports that CRP stimulated phagocytosis of Diplococcus pneumoniae, Staphylococcus aureus, Escherichia coli and Klebsiella aerogenes.
Gupta et al., J. Immunol., 137, 2173-79 (1986) teaches that CRP has been detected in immune complexes isolated from the sera of patients with acute rheumatic fever. Rheumatic fever is an acute inflammatory disease that may follow group A streptococcal pharyngitis. The other components of the immune complexes included streptolysin O and antibodies to streptolysin O.
However, Ballou et al., J. Lab. Clin. Med., 115, 332-38 (1990) teaches that highly purified CRP does not bind to immunoglobulin (monomeric or aggregated) or immune complexes. The article suggests that the reported presence of CRP in immune complexes may result from, or be facilitated by, an association of CRP with components of the immune complexes other than immunoglobulin, such as antigens or complement components.
Kilpatrick and Volanakis, J. Immunol., 134, 3364-70 (1985) reports that there is a CRP receptor on stimulated polymorphonuclear leukocytes (PMN). The authors also disclose that the ingestion of erythrocytes coated with pneumococcal C-polysaccharide and CRP by activated PMN is greater than ingestion of erythrocytes coated only with pneumococcal C-polysaccharide. Finally, the authors propose that CRP's function relates to its ability to specifically recognize foreign pathogens and damaged or necrotic host cells and to initiate their elimination by 1) interacting with the complement system or 2) interacting with inducible phagocytic receptors on neutrophils.
James et al., Dissertation Abstracts International, 41/08-B, 2963 (1980) teaches that CRP binds to a subset of mononuclear leukocytes, including 40% of the phagocytic monocytes and 3% of lymphocytes. Binding was influenced by several factors, including the form of the CRP molecule (i,e., modification of the CRP was required, either by complexing to a ligand or by heating to 63.degree. C.).
Tebo et al., J. Immunol., 144, 231-38 (1990) teaches the presence of a receptor for CRP on monocytes. The article further discloses that a membrane receptor for CRP has been reported on neutrophils.
Kempka et al., J. Immunol., 144, 1004-1009 (1990) discloses results which the authors interpret to mean that CRP is a galactose-specific binding protein which, when associated to the surface of liver macrophages, functions as a receptor mediating galactose-specific endocytosis of particulate ligands.
CRP is a pentamer which consists of five identical subunits. The pentameric form of CRP is sometimes referred to as "native CRP." In about 1983, another form of CRP was discovered which is referred to as "modified-CRP" or "mCRP". mCRP has significantly different charge, size, solubility and antigenicity characteristics as compared to native CRP. Potempa et al., Mol. Immunol., 20, 1165-75 (1983). mCRP also differs from native CRP in binding characteristics; for instance, mCRP does not bind phosphorylcholine. Id.; Chudwin et al., J. Allergy Clin. Immunol., 77, 216a (1986). Finally, mCRP differs from native CRP in its biological activity. See Potempa et al., Protides Biol. Fluids, 34, 287-290 (1986); Potempa et al., Inflammation, 12, 391-405 (1988).
The distinctive antigenicity of mCRP has been referred to as "neo-CRP." Neo-CRP antigenicity is expressed on:
1) CRP treated with acid, urea or heat under certain conditions (described below); PA1 2) the primary translation product of DNA coding for CRP (preCRP); and PA1 3) CRP immobilized on plastic surfaces. Potempa et al., Mol. Immunol., 20, 1165-75 (1983); Mantzouranis et al., Ped. Res., 18, 260a (1984); Samols et al., Biochem. J., 227, 759-65 (1985); Chudwin et al., J. Allergy Clin. Immunol., 77, 216a (1986); Potempa et al., Inflammation, 12, 391-405 (1988).
A molecule reactive with polyclonal antibody specific for neo-CRP has been identified on the surface of 10-25% of peripheral blood lymphocytes (predominantly NK and B cells), 80% of monocytes and 60% of neutrophils, and at sites of tissue injury. Potempa et al., FASEB J., 2, 731a (1988); Bray et al., Clin. Immunol. Newsletter, 8, 137-140 (1987); Rees et al., Fed. Proc., 45, 263a (1986). In addition, it has been reported that mCRP can influence the development of monocyte cytotoxicity, improve the accessory cell function of monocytes, potentiate aggregated-IgG-induced phagocytic cell oxidative metabolism, and increase the production of interleukin-1, prostaglandin E and lipoxygenase products by monocytes. Potempa et al., Protides Biol. Fluids, 34, 287-290 (1987); Potempa et al., Inflammation, 12, 391-405 (1988); Chu et al., Proc. Amer. Acad. Cancer Res., 28, 344a (1987); Potempa et al., Proc. Amer. Acad. Cancer Res., 28, 344a (1987); Zeller et al., Fed. Proc., 46, 1033a (1987); Chu et al., Proc. Amer. Acad. Cancer Res., 29, 371a (1988).
Chudwin et al., J. Allergy Clin. Immunol., 77, 216a (1986) teaches that mCRP can have a protective effect in mice challenged with gram-positive type 7F S. pneumoniae. Mice were injected intravenously with saline, native CRP, or mCRP. Thirty minutes later the mice received a lethal dose of S. pneumoniae. Survival at 10 days was as follows: 2/18 mice pretreated with saline; 7/12 mice pretreated with 200 .mu.g of native CRP; 12/18 mice pretreated with 10 .mu.g mCRP; and 5/6 mice pretreated with 100 .mu.g of mCRP. The authors speculate that CRP may be protective against bacterial infections by mechanisms other than phosphorylcholine binding and that CRP may have a wider role in bacterial host defenses than previously suspected through mCRP (which does not bind phosphorylcholine).
To Applicant's knowledge, there have been no reports that mCRP is protective against any other kind of bacterial infection. Moreover, to Applicant's knowledge, there have been no reports of mCRP binding to viruses, contributing to the phagocytosis of viruses, otherwise being able to neutralize viruses, or being used to treat viral infections.
For a brief review of CRP and mCRP, see Gotschlich, Ann. N.Y. Acad. Sci., 557, 9-18 (1989). Kilpatrick and Volanakis, Immunol. Res., 10, 43-53 (1991) provides a recent review of CRP.
Finally, Applicant wishes to draw attention to certain co-pending applications on which he is named as a co-inventor. U.S. application Ser. No. 07/582,884, filed Oct. 3, 1990, relates to the use of mCRP to bind immune complexes. This application was filed as a national application of PCT application US89/01247 (published as WO 89/09628 on Oct. 19, 1989) and is a continuation-in-part of U.S. application Ser. No. 07/176,923, filed Apr. 4, 1988, now abandoned. Applicant is also named as a co-inventor on U.S. application Ser. No. 07/374,166, filed Jun. 29, 1989, a continuation-in-part of application Ser. No., 07/372,442 filed Jun. 27, 1989, now abandoned. This application describes and claims monoclonal antibodies selectively reactive with epitopes found on native CRP, mCRP or both. Finally, being filed on even date herewith is an application entitled "Method Of Treating Non-Streptococcal Bacterial Infections" which relates to the use of mCRP to treat such infections.